Results 1 to 9 of 9

Thread: '92 K75 starter relay

  1. #1

    '92 K75 starter relay

    I have a 92 K75 with 30,000 miles. A month ago, I took apart the ignition switch and cleaned it and replaced.

    I replaced the battery with a smaller one (my error) but the bike still started and ran. About 20 miles out, the starter motor started running so I shut the bike off and was able to disconnect the battery before the starter motor burned up. Online, I find out the starter relay welded shut due to low voltage.

    Ordered a new battery and relay and installed. My battery charger was lent out so I just hit the starter button. The bike ran for about 2 minutes, the red battery light came on and . . . the starter motor started spinning. Disconnect battery. It had a 12.6 voltage.

    Ordered 2 relays, and installed one with fully charged battery @ 13.6 volts.

    Hit the starter, bike started and 10 seconds later the red battery light came on but I shut the bike down ASAP. Battery voltage down to 12.6 volts.

    Any ideas?? Alternator?

  2. #2
    Liaison 20774's Avatar
    Join Date
    Sep 2005
    Location
    San Antonio, TX
    Posts
    19,304
    Not sure I really understand the concerns for the battery. A reading of 12.6v is not out of the ordinary. A fully charged battery is going to be around 12.7v or so...it can't be 13.6v unless you take a battery measurement immediately after removing the charger. There will be a static charge on it before it drains off relatively quickly.

    Have you read the battery voltage while cranking the engine as well as when the engine is running at say 3000 RPM? That should let you know the health of the battery and charging system.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  3. #3
    3 Red Bricks
    Join Date
    Jan 2007
    Location
    Pleasanton, Ca.
    Posts
    4,551
    Your symptoms are not the usual symptoms of a low battery causing the welding of the starter relay contacts. Normally, when relay contacts get stuck, it is DURING the act of starting the bike. If they don't get stuck during starting there is no signal to engage the starter while you are riding.

    The fact that you state that the starter engaged by itself after it had properly disengaged after you started it, leads me to suspect the starter button. Did you also clean it when you cleaned the ignition switch? If so, it probably didn't get reassembled correctly.

    As Kurt previously stated, the 13+ voltage that you noted on your battery is just the result of just taking it off the charger. Normal voltage is around 12.6 - 12.7.



    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  4. #4
    Registered User kioolt's Avatar
    Join Date
    Apr 2003
    Location
    Maryland
    Posts
    651
    On the early k-bikes even if the starter button is pushed while the engine is running the starter relay will not activate because the ECU turns off the ground side of the starter relay. The starter button supplies +12volt. The relay won't work without both. This would hold true even if the button is damaged, stuck or purposely being pressed.
    2004 R1150RT 186,800 miles , 1991 K100LT 128,700 miles, 1982 R100RT 106,900 miles
    Total 422,400 BMW miles
    AMA,BMWRA,BMWMOA
    The cheapest thing on a BMW is the nut that connects the handlebars to the seat.

  5. #5
    3 Red Bricks
    Join Date
    Jan 2007
    Location
    Pleasanton, Ca.
    Posts
    4,551
    Quote Originally Posted by kioolt View Post
    On the early k-bikes even if the starter button is pushed while the engine is running the starter relay will not activate because the ECU turns off the ground side of the starter relay. The starter button supplies +12volt. The relay won't work without both. This would hold true even if the button is damaged, stuck or purposely being pressed.
    That is correct!

    And I knew that. It just seems the older I get the more trouble I have remembering all the things I know.. I use the starter button, with the engine running, to give me an idea about the mixture since pressing the starter button also enrichens the mixture.

    Based on that, I don't have any idea how, with a new relay, the starter would start to turn minutes after the starter has disengaged.




    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  6. #6

    Starter relay

    I took the new battery to Auto Zone and had it tested as - good.

    Re-installed fully charged, cleaned all contacts on alternator and starter and battery cables, hooked it up and started engine and ran it around 3,000 rpm. No problem. Put covers and guards back on, replaced seat and Took it outside, closed garage doors.

    Sunglasses on, started bike and noticed slight glow of battery light so revved it to 3,000 - 4,000. Light got brighter and . . . starter motor engaged.

    Shut off bike, grabbed needlenose vice grips and loosened positive cable and removed to stop starter motor.

    Burned up another relay. @$89 this is starting to *#!! me off. WTF?

  7. #7
    Registered User mlytle's Avatar
    Join Date
    Oct 2015
    Location
    alexandria, va
    Posts
    238
    doing the same thing over and over again and expecting different results is the definition of insanity.

    it ain't the batter or the relay. have you checked the alternator and all the wiring connections and grounds yet?
    Marshall
    92 K75s
    94 K75s
    09 K1300s

  8. #8
    3 Red Bricks
    Join Date
    Jan 2007
    Location
    Pleasanton, Ca.
    Posts
    4,551
    It sounds like the small wires on the relay is getting power from someplace when it shouldn't and that is pulling in the relay. Try checking voltage to the small terminals on the relay before you do anything else. Hook up your meter to those wires then hook up battery and see if there is voltage there.

    Have you checked that the large contacts on the latest (and previous) relays are indeed engaged once you remove all the wires from them?



    LONG MAY YOUR BRICK FLY!

    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  9. #9
    This is screaming a short in the wiring harness, allowing current to reach the +12v wire to the relay coil someplace downstream from the starter push button switch.

    Lee is, as usual, correct in suggesting a way to trouble shoot the issue.

    First, at the relay disconnect both "big" wires: the one from the battery and the one to the starter. Then with the key turned on test the wire that energizes the relay coil. If you find voltage there it confirms a short to that wire.

    You could also test to see if when the small connector is attached you find continuity between the two large lugs on the relay (with their wires disconnected of course). If you find continuity here without the starter button pushed then disconnect the small connector and see if the relay disengages.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://web.bigbend.net/~glaves/

Similar Threads

  1. Starter Relay
    By arhd63 in forum Airheads
    Replies: 14
    Last Post: 10-07-2016, 01:18 AM
  2. Need starter relay for '73 R75/5
    By DrPaul in forum Airheads
    Replies: 18
    Last Post: 12-31-2014, 03:05 PM
  3. 73 R60/5 Starter Relay
    By 67972 in forum Airheads
    Replies: 10
    Last Post: 05-09-2014, 01:59 PM
  4. K75 Starter Relay
    By JOECUBANA in forum Flying Brick K-bikes
    Replies: 12
    Last Post: 06-24-2007, 10:24 PM
  5. Where is the starter relay? K75
    By 41077 in forum Flying Brick K-bikes
    Replies: 7
    Last Post: 07-08-2006, 05:26 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •